It’s actually amazing to me that a technology like these batteries is as prevalent as it is given the inherent dangers. I get the sensitivity to “advice” being potentially dangerous, but honestly this entire forum should be regarded with a “buyer beware” attitude regardless of who posts it. There are no guarantees, if you’re gonna mess with this stuff you had better pay attention. With that mindset, the above has been great entertainment.
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Can we just archive the last 300 posts of this thread for prosperity.
Thank u pls
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I wish chargers had a programmable tail current shut off.
When Amps taper to 0.1C at 4.2 volts per cell, or what is specified by manufacturer, they actually shut off, instead of holding that voltage forever, green light aglowing.
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Nah, admins have confirmed that this thread is not for any kind of truth and that everything here is just opinion and they will not take any stances.
No one should use this thread as a method in which to learn to make or repair batteries.
I thought the green light indicates it’s shut off? My charger kills the cooling fan at that point, and it also shows a green light when it’s not plugged into a board at all
I can’t speak for your charger.
An ammeter could.
Voltage is one thing, how much amperaGe flows at thaT voltage is where many more details lay.
Most cells specify a terminal amperage @4.2v volts per cell.
0.05C, or thereabouts.
Will gladly defer to Mooch, and delete anything not approved.
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Unfortunately, it depends on the charger. A green light could mean…
…power to the charger is on.
…the charger has completed a charge and has shut off current.
…the charger is doing a bulk charge and there are no errors/faults.
…the charger is in the “top off” stage (CV phase) of charging.
Whether the light is blinking or not might be used to indicate something too,
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Whats up guys, ive lurked through this thread for quite a while and appreciate the absolute wealth of knowledge you guys have provided here. This question may have been answered before but how many welds is too many? I have built a 20s2p 18650 and now building and 20s2p 21700 split pack for onewheels.
I have been doing 3 on the 18650 build and now 4 on this 21700. Also how do they look hot cold pretty good? The 18650 20s has held up great so far, about 500 miles on that battery and have checked on it a few times now welds are holding and everything is balancing and looking good so i think i got it pretty well dialed…
Thanks guys! And gals!
I’m getting a battery build with a local builder, it’s looking much better than the last time. The build is gona be beautiful, hope to post a build thread soon.
Hello everyone, this is my first attempt to build a battery pack (after so much reading and watching tutorials)
I’ve opted for a 12s3p in a slanted 12 cells configuration, and using these custom printed assembly system that I’m very proud of, it makes extremely easy to line up and push the cells together. The result is compact and solid and no glue is needed!
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Now it’s time to connect the P groups, and I initially planed to use the pre-cut slanted nickel strips but the offset of the mounting, even if is minimal, it’s enough for misalignment. They also provide less conductivity for no real gain compared to stacked strips, don’t you think?
Since I’m having difficulties at sourcing nickel sheets (here in Italy) do you think is ok to layer several strip together like this?
And similarly across the single packs? Would a single 1.5mm nickel strip be enough?
Or I’m better off using a 8AWG wire to cross each individual packs?
I plan to fish tape and Kapton tape the whole three packs so the wire is not really necessary for flex.
Other small questions:
- Can I use other material other then the so called fish-tape? Can I use self adhesive PVC sheets?
- Is it necessary to use external termoretractile wrappers if I put the battery inside a case? I’m asking because I wonder the wrapper would act as a barrier for cooling the batteries, and I don’t see it if, for example, I open up a premade commercial battery (say for an ebike). Do people use wrappers for added waterproof safety?
- What fuses should I use?
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This soldering looks a bit suspect to me. Maybe its a bad pic but joints look cold and also looks like solder is wicking up the wire which will cause a higher potential for failure. What is the spec for this battery? I.e. how many amps will you be pushing, how many cells in parallel etc…
How do you balance single cells before placing them in the battery pack?
Power bench?
If they’re new cells they should already be balanced. Typically, they’ll all be around 3.55v from the manufacturer.
If they’re salvaged or used, the process is more complicated. Are they new and if so, where did you get them?
Looks unleaded to me?
Ideal would be to throw them all in parallel. If the voltage difference is low enough between them maybe nichrome wire between would balance slowly.
Use a fuse on the charge port that’s rated to at least the voltage of the pack (50.4V in this case), and a little higher than the current you intend to charge at. If you plan to charge at say 10A then a 12-15A fuse seems reasonable. The guidance from digikey (electronic components seller) is 1.33x.
Don’t use a fuse on the discharge lead (power going from the battery to the ESCs). A fuse here will indeed protect the battery from an overcurrent situation, but it’ll cut all power to the board, including brakes. You want brakes, being able to stop a board so you don’t die is more important than being able to potentially save the battery after a crash
I’m in Ireland and haven’t found a convenient source in Europe, I just order from AliExpress. There’s a thread somewhere here of vendors that users have bought from. The term “nickel strip” tends to turn up more easily in searches than “nickel sheet”, if that’s any help. There is a UK based seller of battery supplies who’s active on the forum, but he can be very very inconsistent with delivery times, even though he’s an otherwise decent guy
8AWG is almost definitely overkill. The received wisdom is that it’s 100% overkill. You may find charts of wire gauge and current ratings online that suggest 8AWG, but that is assuming a much much longer piece of wire. They calculate an acceptable voltage drop for runs of wire in a specific application, often building construction. 12AWG is the norm for eskate batteries because the voltage drop is much lower over a 200mm span than 10-50m
I’m much less confident about this, so bear that in mind. I believe any extra insulation provides additional abrasion resistance, fishpaper is particularly good but PVC shrink is better than nothing. I also believe that a big chunk of the heating effect in packs is from neighbouring cells, and that unless there’s forced airflow it’s unlikely to get a significant amount of cooling with or without an extra layer of insulation
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I’ve learned something new… but I don’t have it at home (maybe the toaster have it inside) Can I use a something commonly found a bit less conductive like a coin?
if is 0.2V difference? Should I put them in parallel before hand? Or should I put them straight to the cell pack and don’t worry at all and let the BMS do the job later? (Molicel P42A)
General warning, don’t listen to Hummie. I’m muting him from here on but just scroll up and see all the times he doesn’t know what he’s talking about
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I challenge u to post what I said that was wrong.
Cant charge a cell that hits 2v or even 1v?
Cc/cv isn’t important as long as cell doesn’t get too much current?
Can’t use a wall watt to charge a cell? (I have many times)
I’m just not getting it. Anyone can list what I got wrong?
You gunna show what I got wrong @jack.luis or just endlessly cry and post poo?
@mr.shiteside show it. Don’t just say it. Do it.
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Plz don’t mute anybody, anyone is enlisted to have their opinions, especially long time contributors like @hummieee, I’ve read several post of him in the past!
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